1. Field of the Invention
The present invention relates to a heat-processing apparatus and method for a semiconductor process in which a plurality of target substrates are subjected to a heat-process simultaneously, i.e., together at the same time. The term xe2x80x9csemiconductor processxe2x80x9d used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target substrate.
2. Description of the Related Art
In the semiconductor process, a vertical heat-processing apparatus is known as a batch type processing apparatus that applies heat processes, such as oxidation, diffusion, annealing, and CVD, to a number of semiconductor wafers together at the same time. The vertical heat-processing apparatus is used such that a number of wafers are arrayed and held with a gap therebetween in a vertical direction in a holder called a wafer boat, and then the holder is loaded into a process chamber of a vertical type. Then, the wafers are subjected to a heat process while they are heated by a heating mechanism disposed around the process chamber.
The heating mechanism includes a surrounding member formed of a cylindrical heat-insulating body, which forms a heating space around the process chamber. A resistance heating wire (heater) is disposed on the inner surface of the surrounding member. Preferably, the heating space comprises a plurality of zones arrayed in a vertical direction, and the heater comprises a plurality of heater segments corresponding to the zones. The heater segments can be controlled independently of each other, so that a heat process is performed uniformly over all the zones.
The heating mechanism is arranged to perform a cooling operation by natural cooling or forcible cooling, which is performed by gas cooling or liquid cooling. As shown in FIG. 5, when the heating mechanism is cooled, the cooling rates of the zones tend to be uneven due to heat discharge and the like. Generally, the cooling rates of the lower and upper zones of the heating space are higher than that of the middle zone. Such unevenness in the cooling rate makes the thermal budgets of wafers in one lot different from each other.
The cooling rate of the heating space is set when the heat-processing apparatus is first installed, using a method so as to adjust the rate of a zone, which tends to have a higher rate, to be closer to the rate of a zone, which tends to have a lower rate. In an apparatus of the natural cooling type, the apparatus is set such that, for example, the heater segments of the lower and upper zones are supplied with a voltage to decrease their cooling rates down to a value as low as the middle zone. In this case, the heat applied to the lower zone warms the middle zone due to convection, radiation, and conduction of the heat, resulting in a decrease in the cooling rate as a whole.
On the other hand, when an apparatus of the forcible cooling type is installed, supply rates of a cooling gas to the zones are adjusted in order to set the cooling rate of the heating space such that the cooling rate of the middle zone becomes almost the same as those of the lower and upper zones. In this case, it is necessary to perform a troublesome operation of repeatedly adjusting manual valves on air supply pipes while confirming the cooling rates of the zones.
An object of the present invention is to provide a heat-processing apparatus and method for a semi-conductor process, which prevent the cooling rates of the zones of a heating space from differing from each other, and increase the cooling rate of the heating space as a whole.
Another object of the present invention is to provide a heat-processing apparatus and method for a semiconductor process, which does not entail the troublesome operation for setting the cooling rate of a heating space when the apparatus is installed.
According to a first aspect of the present invention, there is provided a heat-processing apparatus for a semiconductor process in which a plurality of target substrates are simultaneously subjected to a heat-process, the apparatus comprising:
a process chamber, which accommodates the target substrates;
a holder, which holds the target substrates with a gap therebetween in the process chamber;
a heater disposed around the process chamber, which heats an interior of the process chamber through a sidewall of the process chamber;
a surrounding member, which surrounds the process chamber and the heater, and forms a heating space around the process chamber, the heating space comprising a plurality of zones juxtaposed in a direction in which the target substrates are arrayed;
a plurality of the temperature sensors, which detect temperatures respectively representing the zones;
a cooling mechanism, which forms flows of a cooling gas respectively in the zones, and cools the zones; and
a controller, which controls the cooling mechanism on the basis of temperatures detected by the temperature sensors when the process chamber is cooled, such that a flow velocity of the cooling gas in a first zone having a lower cooling rate becomes higher than a flow velocity of the cooling gas in a second zone having a higher cooling rate used as a reference, thereby adjusting the cooling rate of the first zone to be closer to the cooling rate of the second zone.
According to a second aspect of the present invention, there is provided a heat processing method in the apparatus according to the first aspect, comprising:
subjecting the target substrates to a heat process, in which the target substrates are held by the holder in the process chamber, and heated by the heater;
performing, after the heat process, a cooling operation to cool the process chamber, in which the controller controls the cooling mechanism on the basis of temperatures detected by the temperature sensors, such that a flow velocity of the cooling gas in a first zone having a lower cooling rate becomes higher than a flow velocity of the cooling gas in a second zone having a higher cooling rate used as a reference, thereby adjusting the cooling rate of the first zone to be closer to the cooling rate of the second zone.
According to a third aspect of the present invention, there is provided a vertical heat-processing apparatus for a semiconductor process in which a plurality of target substrates are simultaneously subjected to a heat-process, the apparatus comprising:
a process chamber, which accommodates the target substrates;
a supply section, which supplies the process gas into the process chamber;
an exhaust section, which exhausts the process chamber;
a holder, which holds the target substrates in the process chamber such that they are stacked one on the other with a gap therebetween in a vertical direction;
a heater disposed around the process chamber, which heats an interior of the process chamber through a sidewall of the process chamber;
a surrounding member, which surrounds the process chamber and the heater, and forms a heating space around the process chamber, the heating space comprising a plurality of zones juxtaposed in a vertical direction;
a plurality of the temperature sensors, which detect temperatures respectively representing the zones;
a cooling mechanism, which forms flows of a cooling gas respectively in the zones, and cools the zones, the cooling mechanism comprising a plurality of supply pipes, which respectively supply the cooling gas to the zones to cool the zones, a plurality of valves respectively arranged on the supply pipes to adjust supply rates of the cooling gas to the zones, and an exhaust pipe, which exhausts the cooling gas from the zones; and
a controller, which adjusts opening degrees of the valves on the basis of temperatures detected by the temperature sensors when the process chamber is cooled, such that a flow velocity of the cooling gas in a first zone having a lower cooling rate becomes higher than a flow velocity of the cooling gas in a second zone having a higher cooling rate used as a reference, thereby adjusting the cooling rate of the first zone to be closer to the cooling rate of the second zone.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.